Method for treating contaminated surface with aldehyde-based surfactant

ABSTRACT

A nonionic surfactant having cyclic 1,3-dioxane and/or 1,3-dioxolane functionality which is irreversibly splittable by lowering the pH of its aqueous solution is useful in various processes requiring the removal of emulsified hydrophobic contaminants or other hydrophobic materials from an aqueous stream. After splitting of the surfactant into its component aldehyde and polyol, the hydrophobic components phase-separate and can be removed from the aqueous stream by routine means.

This application is a divisional of prior U.S. application Ser. No.09/261,371, filed Mar. 3, 1999, now U.S. Pat. No. 6,051,035, issued Apr.18, 2000, which is a divisional of prior U.S. application Ser. No.08/985,006, filed Dec. 4, 1997, now U.S. Pat. No. 5,919,372, issued Jul.6, 1999, which is a divisional of prior U.S. application Ser. No.08/439,964, filed May 12, 1995, now U.S. Pat. No. 5,744,065, issued Apr.28, 1998.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to nonionic splittable surfactants and their usein industrial, commercial, and institutional applications which processaqueous streams, typically effluent streams, bearing water-insoluble,oily or waxy contaminants/impurities, including fats, oils and grease(FOGs), total petroleum hydrocarbons (TPHs), and other such hydrophobicmaterials. This invention provides compostitions and methods designed toallow treatment of said aqueous streams to remove such hydrophobicmaterials. These aqueous streams generated during processing containsaid contaminants which are held in the form of a relatively stableemulsion by the action of said surfactants. The contaminants may beremoved from the aqueous effluent by acidifying the waste water,resulting in a release of said contaminants. Specific examples of saideffluents include spent laundry wash water, contaminated oil/wateremulsions from metalworking processes, aqueous streams from textiledyeing, aqueous wash streams from metal (vehicle) cleaning operations,waste or recycle streams from deinking processes, etc.

2. Discussion of the Prior Art

Direct discharge of contaminants or discharge of contaminants to aPublic Owned Treatment Works (POTW) presents significant problems tonumerous industries, e.g., industrial laundries, metalworking, foodprocessing, metal cleaning, etc., which generate large volumes ofaqueous effluents containing FOG, TPH, and/or other emulsified oils(organics) commonly referred to as oily waste-water. Discharge ofaqueous waste steams to a POTW or direct disposal of wash solutions intowaterways, must be done in compliance with environmental regulationstandards. In order to meet these requirements, the waste streamgenerally undergoes pretreatment to reduce the contaminants (e.g., FOGs,TPHs, etc.) so discharge compliance may be accomplished. In the case ofindustrial laundry operations, this problem is of particular concern aslarge volumes of laundry waste-water are generated containing a varietyof contaminants. These contaminants are removed from the soiled fabricsduring the wash process and become associated with the surfactantutilized to hold the impurities in aqueous solution to form relativelystable emulsions.

Metalworking fluids are used to provide cooling and lubrication duringthe many cutting, grinding and forming operations that are used duringprocessing. Metalworking formulations are complex mixtures which containadditives to perform various functions, e.g., emulsification, corrosioninhibition, lubrication, coupling, defoaming, wetting, dispersing, etc.Surfactants are primarily used in metalworking formulations asemulsifiers, wetting agents and corrosion inhibitors. In order tominimize the discharge and the need for waste treatment (cost savings),the fluids are constantly recycled for an extended time. After a periodof use, however, the effectiveness of the metalworking fluids becomessignificantly less due to contaminants which are introduced to the fluidfrom the process operations. These include such impurities as machineoil (often referred to as tramp oil), metal particles, anionic salts,cations, and other foreign matter which have collected in themetalworking fluid. These fluids are then discharged to holding tankswhereby numerous treatment technologies are employed to remove oils(some of which are recycled) and greases to allow the aqueous phase tomeet the required local pretreatment ordinances (typically oil andgrease concentrations of less than 100 mg/l). One of the treatmenttechnologies involves chemical emulsion (oil/water)-breaking, whereby anemulsion-breaking agent e.g., alum or a polyelectrolyte, is added tofacilitate phase separation. This process works by neutralizingelectrical charges which aid in the emulsification of the oil droplets.Typically, anionic surfactants (those surfactants bearing a negativelycharged ion which carries the surface active properties), e.g., soaps,petroleum sulfonates, and the like, are used in metalworkingformulations due to this ability to be charge neutralized (thusdestroying surfactant properties). Anionic surfactants have undesirableproperties, e.g., foaming and lack of hard-water stability vis-a'-visnonionic surfactants; however, nonionic surfactants bear no charge andare not amenable to this type of chemical emulsion-breaking.

Hard surface cleaning formulations are used to clean hard, usuallysmooth surfaces, e.g., metals, ceramics, etc., of process fluids, oil,dirt, debris, etc. Alkaline cleaners are commonly used for aqueoussystems and surfactants are used as wetting agents and dispersants. Hardsurface cleaning may be done by immersion or spraying. The surfactantsshould be stable to an alkaline pH and be low foaming. After severalcleaning operations, the cleaning chemicals have accumulated sufficientcontaminants (e.g., oils) to limit the effectiveness of the surfactantto remove them from the cleaned surfaces, e.g., metal parts, ceramictiles, and the like, and prevent redeposition (through emulsification).Additional surfactant may be added to mitigate this problem; however,the additional surfactant increases the likelihood of undesirable foamgeneration, and makes waste treatment (oil/water emulsion) moredifficult when the bath is discarded. Alkylphenol ethoxylates (e.g.,Triton® X-100, sold by Union Carbide Corp., Danbury, Conn.) are known tobe good surfactants for metal cleaning operations; however, thesematerials are difficult to waste-treat since they are nonionic.

Deinking formulations are used to remove printing ink from oldnewspapers, magazines, business paper, etc. In one of the processes,referred to as the “washing” process, the printed waste paper isfiberized in an alkaline environment, under elevated temperatures, andmechanical stirring in the presence of deinking formulations. Variouswashing stages are employed to obtain a thick suspension of pulp fibersthat are largely free of ink. Surfactants are used in deinking processesas wetting agents to aid in dispersing the inks and binders, and asemulsifiers. Alkylphenol ethoxylates and primary and secondary fattyalcohol ethoxylates are commonly used due to low foaming and gooddispersion properties. Effluent from the washing process which containsthese surfactants has emulsions/dispersions (e.g., ink in water) whichmust be waste-treated. Additionally, recycled water streams from theprocess need to be treated.

The textile industry also generates several waste water effluent streamsfrom their processes. For example, during scouring (a cleaning process)of man-made fibers, surfactants are added to remove chemical adjuncts(e.g., lubricant oil) which remain on the fiber, Surfactants are usedfor detergency and dispersion of the scoured-off particles. Alkylphenolethoxylates are commonly used due to low foaming and good dispersionproperties. Effluent from the washing process which contains thesesurfactants has emulsions (e.g., oil in water) which are difficult towaste-treat. In addition, in a dispersion dyeing process, surfactantsare employed to disperse the water-insoluble dyes to ensure uniformdistribution in the dye bath. When these baths must be discarded, theresultant dispersions are difficult to waste-treat.

In a process known as tertiary oil recovery, oil deposits which remainafter primary and secondary oil recovery are extracted. In the chemicalflooding of the deposits. chemicals are added to water to aid in therecovery. Among these are surfactants which are used to reduce theinterfacial tension between the oil and the water. Thus, the surfactant(and sometimes a co-surfactant) generates an emulsion with the crude oiland the water, which allows the oil to be removed from the deposit. In amicellar flooding process the surfactant with crude oil is pumped intothe oil deposit for several days to extract additional crude oil.Generally, anionic surfactants (e.g., petroleum sulfonates, ethersulfates, ether carboxylates, etc.) are employed.

The above-mentioned uses for the compounds described hereinafter in theinstant invention are not intended to be exclusive, but rather toillustrate the problem and the need for this invention for industrial,institutional, and commercial processes which generate aqueous wastestreams containing FOGs, TPHs, and other water-insoluble contaminantswhich are emulsified due to the presence of surfactants.

One of the desirable properties of an effective surfactant is toefficiently emulsify water insoluble components. However, the separationof these components which might now be considered impurities and othercontaminants from the aqueous effluent is complicated by the emulsifyingproperty of the surfactant. Therefore, the stronger or more efficientthe surfactant in removing and suspending hydrophobic compounds inaqueous solution, the more difficult is the later separation of thehydrophobic impurities from the water.

What is needed by businesses and industries utilizing surfactants inprocess streams which are eventually discharged to the environment is ahighly effective surfactant which first may be utilized as aconventional surfactant to emulsify hydrophobic agents and suspend themin water, and then is capable of modification so as to permanentlyreduce or remove its surfactant ability and permit release, separation,and collection of the previously suspended hydrophobic constituentsassociated with the surfactant.

This problem has been addressed in the industrial laundry industry inpart by the use of amine-based surfactants and various improvedprocesses based on their use. These processes are generallycharacterized by treatment of the aqueous stream bearing the amine-basedsurfactant with the emulsified hydrophobic contaminants with an acid todeactivate the surfactaht and release the hydrophobic contaminants,which then agglomerate and are removed, usually by a skimming or otherphysical separation process. Typical processes are disclosed in U.S.Pat. Nos. 5,076,937; 5,167,829; 5,207,922; and 5,374,358, among others.Amine-based surfactants have not proven to be fully satisfactory,however, since their detergency is below the best surfactants commonlyused in laundry applications, e.g., nonyl phenol ethoxylates (NPE),generally considered to be the standard of the industry. Moreover, theamine-based surfactants tend to re-form and regain their surfactancywhen the pH is raised, e.g., to neutralize the stream prior to dischargeto a POTW which may cause problems down-stream (e.g., foaming).

SUMMARY OF THE INVENTION

It has been found by the present invention that superior end-useperformance combined with desirable surfactant splittability isexhibited by certain acetal-based surfactants which within an alkalineor high pH environment act as nonionic surfactants. However, in anacidic environment these surfactants undergo, due to the presence of theacetal chemical functionality, a chemical splitting of the hydrophobeportion of the surfactant from the hydrophile portion, which destroystheir surfactant properties thereby breaking down their association withthe hydrophobic constituents and allowing them to more easily separatefrom the aqueous phase. This actual bond-breaking process, which affordsa hydrophobe portion and a hydrophile portion, is hereinafter referredto as “splittable,” and the acetal-derived surfactants amenable to thischemical splitting as “splittable surfactants.” Moreover, contrary tothe prior art amine-based surfactants, which are generally regarded as“reversibles,” the present surfactants do not re-form into surfactantswhen the pH is again raised to the alkaline range.

In broad terms, the instant invention provides a splittable, nonionicsurfactant conforming to either of, or mixtures of, the formulas below,and a method for removing impurities associated with such a surfactantin an aqueous stream, comprising:

(a) deactivating the surfactant to release the impurities fromassociation with the surfactant by adjusting the pH of the aqueousstream to an acidic pH sufficient to split the surfactant irreversiblyinto a relatively water-insoluble fraction and a relativelywater-soluble fraction, the released impurities and the water-insolublefraction of the surfactant forming a relatively water-insoluble phase;and

(b) removing at least a portion of the water-insoluble phase from theaqueous stream,

wherein the splittable, nonionic surfactant is represented by either of,or mixtures of, the formulas:

 or,

of which R is hydrogen and R′ is the residue of an organic compound(substituted or unsubstituted) derived from an aldehyde of the formula

wherein R is hydrogen and R′ is the residue of an organic compound(substituted or unsubstituted) which contains a total of about 8 toabout 20 carbon atoms; X is hydrogen or the residue of a hydrophobicend-cap; Y is hydrogen, methyl, ethyl, or mixtures thereof; Z ishydrogen, methyl, or ethyl; m is 0 or 1; and n is an integer of 1 toabout 40.

DETAILED DESCRIPTION OF THE INVENTION

This invention pertains to the purification of commercial, industrialand institutional waste water streams in order to bring them intodischargeable compliance with environmental standards. While thecompositions and methods of this invention have broad applicability inthe industries and uses mentioned above, the invention will be describedfor convenience principally in terms of its extremely effectiveapplicability to industrial laundry processes. It will, of course, beunderstood by those skilled in the art that beneficial results can alsobe obtained in numerous other industrial applications, with formulationadjustments as and if needed.

As indicated, in a preferred embodiment, the invention provides a methodfor removing contaminants, such as FOGs and TPHs, e.g., from laundrywaste water effluents on a batch or continuous basis. During thetreatment process, the contaminants disposed within the textiles to becleaned are treated with an alkaline detergent containing a splittablenonionic surfactant of the type described. herein causing theiremulsification or otherwise causing an association between thesurfactant and contaminants. The surfactant is split by acidification ofthe waste water effluent, destroying the emulsification propertiesassociated with the surfactant, and thus allowing the contaminants tophase-separate from the water. The FOGs, TPHs, and other contaminantsare then removed from the waste water by conventional methods (e.g.,skimming, chemical treatment, dissolved air flotation, etc.). Thelaundry waste water is then dischargeable to the POTW after a final pHadjustment that conforms the waste effluent to environmentalregulations.

More particularly, this invention relates to a method for removingimpurities in aqueous effluents associated with certain pH-receptive,splittable, nonionic surfactants. It is known that anionics, cationics,and amphoteric surfactants which contain charged ions can be neutralized(i.e., lose surfactant properties) by adjusting the pH of the mixture;however, this does not work for conventional nonionic surfactants, otherthan certain amine-based surfactants, since they do not carry a chargedmoiety. According to the present invention, it has been found thatcertain cyclic acetals having a pendant hydroxyl group can function asthe hydrophobe portion of a pH-splittable surfactant. This material canbe alkoxylated or otherwise modified to give a surfactant with a widerange of HLBs and having performance properties which are surprisinglysuperior to those exhibited by other surfactants of related chemicalstructure.

The surfactants useful in this invention have been broadly described inthe art, particularly U.S. Pat. Nos. 3,948,953 and 3,909,460, as well asPolish Temporary Pat. Nos. 115,527 and 139,977. The present inventionimproves upon the teachings of the art, however, by providing optimizedmolecular structures and by expanding their application to diverseend-uses for which such surfactants have heretofore been unknown. In thearea of laundry, especially industrial laundry, surfactants of thisinvention offer the suprising advantages of cleaning performanceequivalent to that of NPE, and significant reduction of environmentallyproblematical materials such as phosphate builders, as will be describedmore fully below. In other end-uses, the surfactants of this inventionoffer the surprising advantages of good oil/water emulsification, metalcleaning, low foaming, and waste treatability of metalworkingformulations.

The pH-receptive, splittable, nonionic surfactants useful in thisinvention comprise acetal-based surfactants derived from condensation ofan aldehyde with a polyol followed by alkoxylation. Specifically, thesurfactants of this invention are represented by either of, or mixturesof, the formulas:

or,

of which R is hydrogen and R′ is the residue of an organic compound(substituted or unsubstituted) derived from an aldehyde of the formula

wherein R is hydrogen and R′ is a residue of an organic compound(substituted or unsubstituted), which contains a total of 8 to 20 carbonatoms, preferably 10 to 18 carbon atoms, most preferably 12 to 15 carbonatoms; X is hydrogen or the residue of a hydrophobic end-cap, e.g.,CH₂Ph, tert-butyl; Y is hydrogen, methyl, ethyl, or mixtures thereof; Zis hydrogen, methyl, or ethyl; m is 0 or 1; and, n is an integer of atleast 1, preferably 1 to about 40, more preferably 2 to about 12, mostpreferably 3 to about 9. As used herein, the phrase “residue of anorganic compound” is contemplated to include all permissible residues oforganic compounds. (By the term “permissible” is meant all residues,moieties, etc., which do not significantly interfere with theperformance of the surfactant for its intended purposes.) In a broadaspect, the permissible residues include acyclic and cyclic, branchedand unbranched, carbocyclic and heterocyclic, aromatic and nonaromaticresidues of organic compounds. Illustrative organic compound residuesinclude, for example, alkyl, aryl, cycloalkyl, heterocycloalkyl,alkyl(oxyalkylene), aryl(oxyalkylene), cycloalkyl(oxyalkylene),heterocycloalkyl(oxyalkylene), hydroxy(alkyleneoxy), and the like. Thepermissible residues can be substituted or unsubstituted and the same ordifferent for appropriate organic compounds. This invention is notintended to be limited in any manner by the permissible residues oforganic compounds.

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds. In a broad aspect, thepermissible substituents include acyclic and cyclic, branched andunbranched, carbocyclic and heterocyclic, aromatic and nonaromaticsubstituents of organic compounds. Illustrative substituents include,for example, alkyl, alkyloxy, aryl, aryloxy, hydroxy, hydroxyalkyl,halogen, and the like, in which the number of carbons can range from 1to about 20 or more, preferably from 1 to about 12. The permissiblesubstituents can be one or more and the same or different forappropriate organic compounds. This invention is not intended to belimited in any manner by the permissible substituents of organiccompounds. It is understood by one skilled in the art that structures(I) and (II) above represent polyoxyalkylene derivatives of the acetal,and may be composed of mixtures of ethoxylates, propoxylates, orbutoxylates produced in either a random or block mode process. Whilethere is no specific known limit on the molecular weight of thealdehyde, as the number of carbon atoms in the aldehyde exceeds about12-15, the resulting surfactant becomes more paraffin-like in nature.Although this could result in better phase separation, such aldehydesare not readily available (in commercial quantities) because of thedifficulty of manufacturing and purifying them.

The splittable, nonionic surfactants of the formula above can beprepared by conventional methods known in the art. (See, e.g., U.S. Pat.No. 3,948,953 and its CIP 3,909,460, as well as Polish Temporary Pat.Nos. 115,527 and 139,977, which refer to the pH-splittability of suchcompounds.) For example, the surfactants of the formulas may be preparedusing polyol starting materials containing at least three hydroxylgroups, two of which form a cyclic 1,3-dioxane or 1,3-dioxolanefunctionality, by treating a polyol with a suitable aldehyde. Examplesof such polyols include, for example, glycerol,2-ethyl-2-(hydroxymethyl)-1,3-propanediol (trimethylolpropane),1,1,1-tris(hydroxymethyl)-ethane(trimethylolethane), sorbitol andmannitol among others. Glycerol and trimethylolpropane are preferred.Examples of suitable aldehydes include 2-ethylhexanal, octanal, decanal,2-propyl heptanal and isomers (from valeraldehyde aldol condensation),undecanal, and dodecanal. Of these, 2-ethylhexanal, 2-propylheptanal,decanal, and dodecanal are preferred. Most preferred is a series ofisomers produced by the “Oxo” reaction of C₁₁-C₁₄ olefins. This materialis available from EniChem Augusta Industriale, Milano, Italy.

The first step in the synthesis of the splittable surfactants of thisinvention is to form the acetal moiety by treating the polyol with thealdehyde under suitable reaction conditions, usually at atmosphericpressure and a temperature of from about 40° C. to about 175° C. in thepresence of an acid catalyst, such as sulfuric or toluenesulfonic acidin an amount of from about 0.01 to about 10, preferably about 0.01 toabout 0.5, weight percent based on the total charge, with removal of,water formed from the condensation reaction. It has been found thatphosphoric acid is also desirable since, although somewhat slower inreaction rate, it produces a somewhat lighter, more desirable color inthe product. The aldehyde is mixed with about a 1.1 to 1.3 molar excessof the polyol. Heptane is added as a solvent to aid in the azeotropicremoval of water from the system. The five-membered ring (1,3-dioxolane)is formed preferentially.

The resulting acetal containing at least one free hydroxyl group issuitable for the alkoxylation reaction, normally conducted under basicconditions, which involves reaction of the acetal with a suitablealkylene oxide such as ethylene oxide, propylene oxide, butylene oxideor mixtures thereof. Conventional reaction conditions may be employed,e.g., temperatures of from about 80° C. to 150° C. and modestly elevatedpressures. Suitable basic catalysts include tertiary amines, sodiumhydroxide, potassium hydroxide and the corresponding metals, hydridesand alkoxides. The resultant acetal-based alkoxylation reaction productsare represented by formulas (I) and (II), above. Typically from about 1to about 100 moles, preferably from 1 to about 40 moles of alkyleneoxide per mole of acetal may be employed.

The splittable, nonionic surfactants of this invention have a broaddistribution of alkoxylation species which is expected from abase-catalyzed alkoxylation process. See, for example, M. J. Schick,Nonionic Surfactants, Volume I, Marcel Dekker, Inc., New York, N.Y.(1967) pp. 28 to 41. The splittable, nonionic surfactants of thisinvention may be produced to have a narrow, but balanced, distributionof alkoxylation species by employing narrow molecular weight catalysts(e.g., calcium-based) which have been disclosed in the art (e.g., U.S.Pat. Nos. 4,754,075; 4,820,673; and 4,886,917). These catalysts producesurfactants which can be relatively free from large amounts ofsubstantially higher alkoxylation moieties, i.e., those having at leastthree more alkoxyl groups than the average peak alkoxylate species.Advantageously, these narrow distributions can be obtained where themost prevalent alkoxylation moiety has four or greater alkoxy units,that is, in the regions in which conventional catalysts provide arelatively wide range of alkoxylation species. It is common for oneskilled in the art to tailor-manufacture an alkoxylate to enhance theend-use performance. The benefit of the narrow molecular weight productscan be determined by evaluation under a given process vis-a'-vis themore conventional distribution obtained under typical (e.g., potassiumhydroxide) base-catalyzed alkoxylations. The moles of alkylene oxideadded to the acetal starter will depend on various factors associatedwith the end-use application, e.g., the desired hydrophile-lipophilebalance (HLB) for emulsification, cloud point, etc. No one alkoxylate ispreferred for all applications, and within a given application a blendof a low mole (e.g., 3-mole) and a high mole (e.g., 9-mole) alkoxylatemay be preferred vis-a'-vis a single product (e.g., 6-mole alkoxylate).In addition, ethylene oxide/propylene oxide/butylene oxide mixtures,whether random or block addition. may show advantages in certainapplications as compared to a material in which only ethylene oxide hasbeen added.

As is well known in detergent formulation art, particularly in laundryapplications, surfactants are typically combined with one or more“builders.” Such materials are added to the composition for variousreasons, including, e.g., sequestering water hardness ions, facilitatingthe removal and suspension of soils and blocking redeposition,maintaining pH in the basic range, and the like. Among the commonly usedinorganic builders are phosphates (e.g., sodium tripolyphosphate),typically used in concentrations of about 5 to about 30 wt. percent,silicates and metasilicates, typically used in concentrations of about 5to about 40 wt. percent, sodium carbonate and bicarbonate, typicallyused in concentrations of about 0 to about 40 wt. percent caustic,typically used in concentrations of about 0 to about 10 wt. percent,zeolites, and the like. Among the commonly used organic builders arecarboxymethyl cellulose (CMC), polyvinyl-pyrrolidone (PVP),ethylenediaminetetraacetic acid (EDTA), citric acid, and the like. Suchmaterials are necessary and are commonly used with conventional nonionicsurfactants such as nonylphenol ethoxylates, primary and secondaryalcohol ethoxylates, and the like. There has been significant pressureon detergent manufacturers to find a replacement for phosphates indetergent compositions due to environmental concerns. To date, this hasmet with only limited success (e.g., nitriloacetic acid as a phosphatesubstitute in household powders) since phosphates not only soften waterbut have other properties (e.g., deflocculate and suspend insolublematerials, emulsify oils, etc.) which aid in the cleaning and removal ofimpurities from the soiled fabrics. It would be desirable to identify acomponent in the detergent composition which would minimize or eliminatethe need for phosphates. It is a surprising feature of the presentcomposition that phosphate builders can be largely or completely avoidedwith little or no effect on cleaning performance. Preferably, phosphatecontent may be limited to no more than about 10%, more preferably 0 toabout 5%, by weight of the total dry detergent formulation. If it isdesired to include one or more builders in the formulation, normalconcentrations of silicates or metasilicates are preferred.

Since a principal purpose of the invention is to permit coalescence oragglomeration of the FOGs into readily removable form, it is desirableto avoid the use of effective concentrations of materials which impedecoalescence, e.g., redeposition aids, such as phosphates, polyacrylates,and CMC. Dispersing aids in general should be used sparingly, andpreferably avoided, to maximize the phase separation which occurs afterthe surfactants of the instant invention are split.

As mentioned previously, metalworking fluids are used principally to aidin the cutting, grinding or forming of metal, to provide a qualityfinish to the workpiece while minimizing wear of the machine tools.These fluids provide cooling and lubrication of the metal/tool interfacewhile aiding in the removal of metal fines and chips from the piecebeing formed. The evolution of metalworking fluids has gone from simpleoils to complex systems based on the emulsification of oils in water. Tothose skilled in the art, the water-based technology types ofmetalworking fluids are generally classified as soluble oils,semisynthetic fluids, or synthetic fluids. Each type of fluid offersdifferent benefits for metalworking. For example, soluble oils, whichare fluids with a high oil content, provide better lubricity vis-a'-vissynthetic fluids. Conversely, synthetic fluids, which are generallywater-soluble and contain no mineral oils, offer better cooling, hardwater stability, and resistance to microbiological degradationvis-a'-vis soluble oils. The third type of metalworking fluid, thesemisynthetics, was developed to take advantage of the benefits of bothsoluble and synthetic oils. These semisynthetics are water-based fluidscontaining some oil-based components emulsified into water to form amicroemulsion system. Thus, it follows that semisynthetic and syntheticmetalworking fluids would be more difficult to waste-treat than thesoluble oils.

As is well known to one skilled in the art, surfactants are combinedwith one or more chemical additives in order to formulate a metalworkingfluid which can serve a multitude of functions. These functions includessuch things as corrosion inhibition, lubrication, defoaming, pHbuffering, dispersing and wetting. These chemical additives includechemical functionalities such as fatty acids, fatty alkanolamides,esters, sulfonates, soaps, chlorinated paraffins, sulfurized fats andoils, glycol esters, ethanolamines, polyalkylene glycols, sulfated oils,and fatty oils. Such additives are necessary and are commonly used withconventional anionic and nonionic surfactants. Metalworking formulationswhich use anionic surfactants are relatively easy to waste-treat sincethese materials are amenable to treatment by acidification or reactionwith cationic coagulants. However, metalworking fluid formulations whichcontain conventional nonionic surfactants are much more difficult towaste-treat since they are not amenable to these types of chemicaltreatment. See, for example, J. C. Childers, Metalworking Fluids, editedby J. P. Byers, Marcel Dekker Inc., New York, N.Y. (1994), pp. 185,367-393. As a result, when using nonionic surfactants (e.g., anonylphenol ethoxylate) as emulsifiers for metalworking fluids,formulations are designed to allow for waste water treatment. In fact,numerous metalworking fluid formulations which use conventional nonionicsurfactants are designed first and foremost to be waste-treatable afteruse. This emphasis on waste treatment results in metalworking fluidswhich may not provide the best possible end-use performance, such ascorrosion inhibition, lubrication, dispersion or wetting. Despite theirdifficulty to waste-treat, conventional nonionic surfactants are stillused in metalworking formulations since nonionics offer distinctadvantages (e.g., hard water stability, “tighter” emulsions, variety ofHLBs, low foaming, etc.) over anionic surfactants. The splittable,nonionic surfactants described herein provide good emulsification andwetting for soluble oils, semisynthetics, and synthetics, whileproviding the added benefit of easier waste-water treatment. Further,with splittable, nonionic surfactants, improved metalworkingformulations can be developed which provide better end-use performancevis-a'-vis metalworking fluids which are designed to be waste-treatable.

Metal-cleaning fluids are used in a variety of metal-forming and coatingprocesses, and are used to clean metal surfaces of process fluids, oil,dirt, debris, etc. There has been a growing trend toward the developmentof aqueous-based cleaning systems, as a number of widely used organicsolvents, such as methyl chloroform, trichloroethylene, methylenechloride, etc., are in various stages of being banned from theworkplace. Aqueous alkaline cleaners, therefore, are increasing in theiruse, and formulations are being developed to maximize their usefulness.Conventional nonionic surfactants (e.g., Triton® X-100) are commonlyused as wetting agents, dispersants and emulsifiers.

A problem typically encountered with metal-cleaning solutions is theaccumulation of oils in the cleaning bath. As the oils increase in thecleaning bath, it becomes more difficult for the surfactant to emulsifythe oil. More surfactant may be added to the bath to remedy thisproblem; however, problems of foaming and waste-water treatment of theeffluent become more pronounced because of the higher amount ofsurfactant present. It would be desirable to have a surfactant whichprovides cleaning, low foaming, and waste-treatability. The prior artU.S. Pat. No. 5,114,607 discloses the use of an ethylene oxide-propyleneoxide block copolymer surfactant and a defoaming reverse ethyleneoxide-propylene oxide block copolymer surfactant as a surfactant in analkaline formulation which provides good metal-cleaning, low foaming,and waste-treatability. In addition, a hydrotrope must be added tomaintain the suspension. After cleaning, the hydrotrope is neutralizedwith acid, which allows for phase separation. This technology may beviewed as similar to the aforementioned reversible surfactants. Thenonionic, splittable surfactants of the instant invention provide lowfoaming, cleaning, and waste treatability which hitherto was unavailablewith the conventional nonionic surfactants. An additional defoamer maybe minimized by the addition of propylene oxide, or other hydrophobicmoieties (e.g., tert-butyl, benzyl, methyl, etc.) to the parentsurfactant. Waste-water treatment can be accomplished as detailed above.Again, suspension agents (e.g., phosphates) should be minimized in thecleaning formulation to favor phase separation.

Similar results may be obtained in other applications, whereby FOGs,TPHs and other water-insoluble contaminants are emulsified inwaste-water effluents by the presence of surfactants. With the use ofthe nonionic splittable surfactants of the instant invention, the pH ofthe waste-water effluent may be lowered (² about pH 6) to initiate thehydrolysis of the acetal which results in the release of a hydrophobeportion and a hydrophile portion, thus resulting in a loss ofsurface-active properties. The net result is a phase separation of oiland water. The nonionic, splittable surfactants of the instant inventionare compatible with other waste-water treatment methods, includingprimary-stage treatments (e.g., gravity separation) and secondary-stagetreatments. The invention described herein, may add significant value tosecondary-stage treatments including membranes (e.g., ultrafiltrationsystems which are often fouled by impurities resulting in significantprocess down-time), centrifugation, and a dissolved air flotation (DAF)unit. The net result is greater throughput and minimal usage ofexpensive waste treatment chemicals.

In accordance with the method of this invention the acetal-derived,splittable, nonionic surfactant is split in an aqueous solution torelease impurities from association with the surfactant by adjusting thepH of the solution to an acidic pH sufficient to cause the acetalfunctionality to chemically break (rupture of two carbon-oxygen bonds)resulting in a hydrophilic fragment and a hydrophobic fragment. Since inmost processes this bond breaking is done in an aqueous environment,this splitting process may also be referred to as an acetal hydrolysis.The pH can be adjusted by conventional procedures using conventionalacids. Suitable acids include, for example, sulfuric acid, hydrochloricacid, acetic acid, hydrofluoric acid, nitric acids, etc. Preferably, thepH of the adjusted solution is from about pH 3 to about pH 6. The amountof acid to be added is an amount sufficient to cause splitting of thesurfactant, and is dependent upon the volume and composition of thesolution. The splittable nonionic surfactants may also be split withwell-known solid heterogeneous acids (e.g., Nafion®, silica gel,Amberlyst®15, mixed metal oxides, etc.). The use of solid heterogeneousacids is especially useful in fixed-bed treatments.

The catalyzed hydrolysis of acetals has been extensively studied in theart. For example, T. H. Fife, Accounts of Chemical Research, Volume 5(1972), pp. 264-272; and, E. H. Cordes and H. G. Bull, Chemical Reviews,Volume 74(1974) pp. 581-603. From these, it is apparent that the rateand reaction conditions necessary to cause carbon-oxygen bond rupture ofthe acetal are complex. While not wishing to be bound by theory, thesplittable, nonionic surfactants of the instant invention may be splitover a wide range of pressures ranging from atmospheric orsubatmospheric pressures to superatmospheric pressures, preferablyatmospheric pressure.

In addition, the temperature of the deactivation may be as low as aboutambient temperature to about 100° C. Generally, temperatures aboveambient result in shorter times for splitting of the surfactant, but inprocesses whereby temperatures above ambient are not preferred (e.g.,for economic reasons), the splittable, nonionic surfactant will. stillhydrolyze. Temperatures of about 40-80° C. are generally preferred.

Chemical components in the waste-water effluent in combination with thesplittable, nonionic surfactants can produce what are hereinafterreferred to as “matrix effects.” These matrix effects may inhibit theready hydrolysis of the acetal moiety and/or interfere with the phaseseparation of the treated effluent. It is expected that the hydrolyticreactivities of the splittable, nonionic surfactants will be less in acomplex matrix composed of numerous chemical components vis-a'-vis thesplittable, nonionic surfactant in water. Conversely, some chemicalcomponents (e.g., silicates) in the matrix may actually aid in thehydrolysis of the splittable, nonionic surfactants, and/or the phaseseparation of the treated effluent.

Treatment of the waste water effluent to split the splittable, nonionicsurfactant and ultimately cause phase separation is conducted for aminimum period of time sufficient to cause hydrolysis or splitting ofthe surfactant, followed by partial phase separation of the organic andaqueous components, which hitherto were emulsified. The exact reactiontime employed is dependent, in part, upon factors such as temperature,matrix effects, degree of agitation, and the like. The reaction timewill normally be within the range of from about one-half to about 10hours or more, and, preferably, from less than about one to about 5hours.

The splittable, nonionic surfactant is split into a relativelywater-insoluble fraction (hydrophobic) and a relatively water-soluble(hydrophilic) fraction. The water-insoluble fraction comprises thestarting aldehyde and the water-soluble fraction comprises analkoxylated polyol. Neither fraction produced from the hydrolysis issurface-active, so the FOGs and TPHs are released from association,e.g., emulsion, with the surfactant. The FOGs, TPHs and the hydrophobicfraction of the surfactant form a relatively water-insoluble phase inthe aqueous stream. At least a portion of this phase in the spentaqueous stream is recovered by conventional methods such as filtration,skimming, and the like. Preferably, a substantial portion of thewater-insoluble phase is recovered, e.g., the spent aqueous stream hasless than 100 parts per million FOG. The recovered water-insoluble phasecan be disposed of, for example, in a landfill or by burning in afurnace, or may undergo oil reclamation processes. The remaining aqueousstream can be discharged to a POTW after a final pH adjustment to arelatively non-acidic pH that conforms the waste effluent toenvironmental regulations, or in some cases be recycled for further use.Recycle is especially attractive if the aqueous stream is furthertreated with a membrane system to remove any water-soluble organics,including the water-soluble alkoxylated polyol which is present afterthe splittable, nonionic surfactant is hydrolyzed. It is anotheradvantage that the splittable, nonionic surfactants of the instantinvention may be used in conjunction with membrane systems to provideessentially organic-free aqueous effluent. By pretreating the aqueouseffluent containing the compounds of the instant invention according tothe methods described hereinabove, an aqueous phase is obtained whichcontains considerably less FOGs and TPHs which can contribute to foulingof membranes. This results in longer membrane life and less downtimeduring waste-water treatment.

The nonylphenol ethoxylates known under the surfactant tradenames asTergitol® NP-4, Tergitol® NP-6, and Tergitol® NP-9 are 4-mole, 6-mole,and 9-mole ethoxylates, respectively. The octylphenol ethoxylate knownunder the surfactant tradename of Triton® X-100 is a 10-mole ethoxylate.The amine ethoxylate known under the surfactant tradename Triton® RW-75is a 7.5-mole ethoxylate. The secondary alcohol ethoxylate known underthe surfactant tradename as Tergitol®15-S-9 is a 9-mole ethoxylate. Theprimary alcohol ethoxylate known under the surfactant tradename asNeodol®25-9 is a 9-mole ethoxylate.

It will also be recognized by those skilled in the art that thecompositions and methods of this invention are not limited to theparticular uses discussed above. For example, it may be expeditious inparticular instances to treat an internal process stream with asurfactant of this invention, effect the separation of susceptiblematerials by a method of this invention, then recycle the remainder ofthe stream to the process. In another variation, a stream bearingmaterials emulsified by a surfactant not of this invention could betreated with a surfactant of this invention to replace in whole or inpart such other surfactant, followed by effecting a separation method ofthis invention, and returning the other surfactant to the process as bya recycle. Similarly, it will be recognized that a method of thisinvention need not result in complete deactivation of the surfactant:for example, sufficient deactivation could be employed to reducecontaminants to an acceptable level and the treated stream returned tothe process until the contaminant level builds up to the point whereadditional treatment is required. Obviously, such a technique could beapplied on either a continuous or batch basis.

In another useful embodiment, a surfactant of this invention can be usedin a method to co-emulsify in an aqueous stream an existing emulsion ofhydrophobic materials with unemulsified hydrophobic materials also insuch stream, and thereafter splitting the resulting co-emulsifiedmaterials by reducing the pH of the stream, according to the methodpreviously described.

EXAMPLES

The invention is illustrated by, but in no way limited by, the followingexamples.

Table 1 General Procedure for the Preparation of Acetals Via theCondensation of Aldehydes with Polyols (Examples A-L)

To a multi-neck, round-bottom flask equipped with a condenser,Dean-Stark trap and heating mantle were added aldehyde, polyol, heptane,and p-tolunesulfonic acid monohydrate. The flask was purged andevacuated three times with nitrogen and the mixture heated to reflux,with concurrent removal of the heptane/water azeotrope until such timeas no additional water was obtained overhead in the Dean-Stark trap. Thereaction mixture was cooled and placed in a separatory funnel to removeunreacted polyol (in the case of glycerol) which separated from thereaction mixture as the bottom layer. Products were refined on a rotaryevaporator under vacuum. In some cases, prior to refining the material,additional heptane was added to the reaction mixture and it wasextracted (using a separatory funnel) 3 times with a 10 percent byweight sodium carbonate/water solution to remove additional polyol andneutralize the catalyst. The aqueous solution (bottom layer) wasdiscarded, and the organic solution was refined as describedhereinabove. Additional refining was required in some cases to giveacceptable purities (³97 percent purity) of the acetal. The acetals wereanalyzed by capillary gas chromatography (FID) using a 30 meter, 0.25 mmID, 0.1 micron film thickness, DB5HT column.

General Procedure for the Alkoxylation of Acetals (Examples A-L) toProduce Acetal-derived Surfactants

The general procedure to produce the base-catalyzed starter was asfollows. The acetal was charged to the reactor or to a round-bottomflask equipped with a water condenser. The catalyst (typically sodiumhydroxide or potassium hydroxide at 0.05-5.0 wt. percent) was added tothe acetal and the mixture was heated at 140° C. under vacuum (10-50mm/Hg) for one hour while removing water overhead. After this time thekettle product was suitable for alkoxylation as described below.

The procedure described herein was used to produce the splittable,nonionic surfactants described in the instant invention. The reactor forthese preparations was a 2-gallon, stirred autoclave equipped with anautomatic ethylene oxide (or other alkylene oxide) feed system wherein amotor valve controlled the feed of ethylene oxide to maintain about 60psig pressure. Into the 2-gallon, stirred autoclave were added theacetal starter (examples A-L), ethylene oxide and a catalyst (eitherperformed as described hereinabove, or generated in situ by heating thecontents and removing the water from the system). Ethoxylations wereconducted under a nitrogen atmosphere (20 psig) at a temperature of 140°C. Propoxylations were done at a temperature of 110-115° C. Theethoxylation was continued until a desired mole ethoxylate (or mixedalkoxylate) was obtained, after which the oxide feed was discontinuedand the contents were allowed to “cook out” (maintain a constant reactorpressure). An aliquot was discharged through the dump valve, allowed tocool, and partly neutralized with acid (e.g., acetic, phosphoric, etc.),being certain to maintain an alkaline pH. The ethoxylation was continuedon the remaining material in the autoclave by continuing the addition ofethylene oxide until the next mole ethoxylate was obtained. Thisprocedure was continued until a product series was obtained (usually a3-, 6-, 9-, and 12-mole ethoxylate).

Procedure for the Preparation of Narrow Molecular Weight Acetal (ExampleA)-derived Surfactants

Into a 1-liter reaction flask equipped with a reflux condenser,thermocouple, mechanical stirrer and a gas purge inlet was added 551grams of the acetal derived from the condensation of 2-ethylhexanal andglycerin (example A), and 5.02 grams of calcium hydroxide. The resultingmixture was heated under vacuum (180 mm) at 80° C. for a period of 2hours while removing water from reaction overhead. The reaction mixturewas then cooled in an ice bath to 7° C. and 4.5 grams of concentratedsulfuric acid was added to the flask. The mixture was stirred for 30minutes and the reaction mixture was heated to 165° C. during which time16 grams of material was removed overhead. The kettle product was thencharged to the 2-gallon autoclave and ethoxylated as describedhereinabove to afford a 6-mole ethoxylate with a narrow molecular weightproduct distribution, vis-a-vis the product made using sodium hydroxideas catalyst.

Testing and Evaluation Procedures

In order to determine the laundry cleaning efficacy of the nonionic,splittable surfactants of the instant invention, standardized procedureswere run using a Terg-O-Tometer and laundry standard surfactants to aidin the evaluation. The Terg-O-Tometer testing allows for a preliminaryscreening of surfactant detergency, and can provide direction forfurther development.

A Model 7243 S Terg-O-Tometer obtained from Research and Testing Co.,Inc. Hoboken, N.J., was used to determine laundry cleaning performanceof the nonionic, splittable surfactants describe herein. Each of the sixbuckets was charged with 1000 mL of distilled water, 2.5 grams ofsurfactant, and sodium hydroxide solution to give a pH of 10.7 to 11.0.Four standard soiled cloths containing the same amount of dirty motoroil soil were added to the bucket. Four clean swatches were also addedfor bulking purposes and to provide a qualitative evaluation forredeposition. The test swatches were obtained from Testfabrics, Inc.,Middlesex, N.J., and Scientific Services S/D, Inc., Sparrow Bush, N.Y.The cloths were laundered for one ten-minute wash step, after which thecloths were removed from the buckets and the buckets rinsed withdistilled water. The cloths were returned to the bucket with 1000 mL ofdistilled water, and one two-minute rinse step was conducted. Wash andrinse temperatures were both 145° F. and the Terg-O-Tometer operatingspeed was 100 rpm. Wash and rinse water were preheated to theappropriate temperature before charging to the bucket. The cloths weredried in a standard household design clothes dryer and evaluated forcleaning performance. A BYK-Gardner TCS Spectrophotometer was used toobtain the reflectance of the soiled cloths before and after laundering.The percent detergency was calculated using the equation:

% Detergency=[(A−B)÷(C−B)]×100

where

A=Reflectance of the soiled test cloth after laundering

B=Reflectance of the soiled test cloth before laundering

C=Reflectance of the test cloth before soiling.

The results are provided in Table A. Test cloths change from lot to lotdue to differences in soiling and the condition and texture of thefabric. Examples 1-9 in Table A were evaluated on the same lot of cloth.Examples 1-5 in Table A were evaluated on the same lot of cloth.Examples 6-11 were evaluated on the same lot of cloth. Examples 12 and13 were run on different lots. Under these circumstances it is best tocompare the results with how it performed against the standard (e.g.,Tergitol® NP-9) under the same conditions. As the results show, severalnonionic splittable surfactants of the instant invention showed improveddetergency vis-a-vis the standard. The 3-mole ethoxylate of acetal A wasparticularly a good performer. When TMP was used as the polyol the bestdetergency was shifted to a higher mole ethoxylate compared to a similaracetal prepared using glycerol as the polyol (examples 1 and 6 versus 4and 7). Additionally, the use of propylene oxide to increase thehydrophobicity of the acetal (example 2) and the use of a narrowmolecular weight catalyst to provide an ethoxylate with a narrowdistribution (example 3) resulted in an improved percent detergency ofthe 6 mole ethoxylate compared to the parent compound (example 1).Branched aldehydes afforded better detergency compared to unbranchedaldehydes of similar molecular weight (examples 1 and 9; 8 and 10). Thesplittable nonionic surfactants derived from higher molecular weightaldehydes gave improved performance compared to those derived from lowermolecular weight aldehydes (examples 12 and 13).

To determine the effect of various and sundry inorganic and organicbuilders on the treatability of the waste water effluent (matrixeffects) of the nonionic splittable surfactants, .compositionscontaining 15-25 weight percent of a splittable nonionic surfactant and75-85 weight percent builder were prepared. Ten grams of built detergentwere added to the Terg-o-Tometer bucket (pH ranged from 9.5 to 11.5depending on the choice and amount of builders) and evaluated using theprocedure described hereinabove. The waste-water effluent was collectedby combining the wash and rinse waters from the standard Terg-o-Tometertest procedure for each bucket, and filtering each through a 35 meshscreen (to remove the larger lint) into a ½ gallon jar. Each compositewas maintained at the wash and rinse temperature (145°) in a constanttemperature bath until time for treatment. Each composited waste waswell agitated then approximately 800 to 900 mL were poured into each oftwo 1 liter beakers. The beakers were modified with a 4 mm Teflon-barrelstopcock located 1½ to 2 inches from the bottom for the purpose ofwithdrawing a water sample as a side stream free of contamination fromfloating oil and floc or settled sludge. The beakers werecustom-fabricated by Lab Glass, Inc., Kingsport, Tenn. The waste-waterin one of the beakers was left unchanged (Untreated Sample). The pH ofthe waste-water in the other beaker (Treated Sample) was lowered to 3 or5 using an aqueous sulfuric acid solution. Both beakers were maintainedat the wash and rinse temperature (145° F.) in a constant temperaturebath for 30 to 90 minutes. The beakers were removed from the bath andallowed to sit undisturbed for 20 to 30 minutes. Water samples(approximately 5 mL) were taken from each beaker through the stopcockafter first gently purging out and discarding approximately 10 to 15 mLto remove contamination from the side arms of the stopcock. The watersamples were then analyzed for Chemical Oxygen Demand (COD) which wasdetermined under limited and controlled conditions described in StandardMethods For The Examination of Water and Wastewater, 18th Edition(1992), procedure No. 5220 D. As the results show (Table B) when highlevels of phosphate (example 1) are in the detergent formulation thephase separation of organics (e.g., FOGs, TPHs, etc.) and water is notgood (as evidenced by the high COD numbers; thereby not allowing for thefull benefit of the instant invention for phase separation of theorganics and water. However, when phosphate is absent in the formulation(examples 2 and 3), good phase separation was observed after thesplittable nonionic surfactant is split by lowering the pH to 3. The useof a conventional nonionic surfactant (e.g., Tergitol® NP-9) does notsplit under these conditions; therefore, no phase separation wasobserved.

The effect of phosphate concentration on cleaning performance of thenonionic, splittable surfactants compared to conventional nonionicsurfactants is provided in Table C. As the results show, good detergencywas obtained when phosphate was in the formulation for the splittablenonionic surfactant (example 1) and the conventional nonionic surfactant(example 4). Unexpectedly, good detergency was maintained forformulations without phosphate when a splittable nonionic surfactant wasused (examples 2 and 3), vis-a-vis poor detergency when phosphate wasabsent in the formulations for a conventional nonionic surfactant(examples 5 and 6).

In order to determine the efficacy of the nonionic, splittablesurfactants for metalworking fluid formulations, emulsification studies,standard foam tests, and waste-treatability data was collected.

Emulsification tests were run simulating a soluble oil formulation. To amixture of 16 grams of naphthenic oil (Ergon Hygold V-200) and 4 gramsof surfactant were added 25 grams of water. Observations were made afterstanding at room temperature for 1 hour and 24 hours. The results aregiven in Table D. As the results show, the splittable nonionicsurfactants of the instant invention afford emulsification propertiessimilar to Tergitol® NP-4 Tergitol® NP-6 and Tergitol® NP-9. The 6 moleethylene oxide adduct of acetals K and L were particularly goodemulsifiers for this test.

The relative foaming properties of the nonionic, splittable surfactantswere determined under limited and controlled conditions described inASTM procedure No. D1173 and are reported in Table E. As the resultsshow, the nonionic splittable surfactants of the instant invention showsignificantly less foam after 5 minutes compared to the standardTergitol® NP-9 (example 12). The acetals derived from lower molecularweight aldehydes were the lowest foamers, and within a given molecularweight aldehydes which have carbon branching gave less foam (examples 1and 3). Within a given family, the lower mole ethoxylates produced lessfoam (examples 7-10).

The waste-treatment of the nonionic, splittable surfactants was comparedto conventional nonionic surfactants in metalworking formulations bytreating a mixture containing metalworking fluid components using thefollowing method:

The mixture to be tested was diluted to 0.5 wt. percent and stored forat least 24 hours at room temperature. After this time, the pH of 0.5wt. percent solution was lowered to a pH of 3-5 with 2.5 wt. percentaqueous sulfuric acid. This acidic solution was then heated to 50-60° C.for 2-10 hours. After allowing the solution to cool to room temperature,it was adjusted to pH 6-9 with 2.5 wt. percent aqueous sodium hydroxide.Up to six 600-mL beakers were filled with 250 mL of the test solution.The mixture was stirred at 95-100 rpm for 5-6 minutes on a Phipps & Birdsix-paddle stirrer with illuminated base. Cationic polymer (WT 2545 fromCalgon Corp., Pittsburgh, Pa.) was added in increments of 50-100 ppm upto a maximum of 1200 ppm while mixing at 95-100 rpm for at least fiveminutes. After this time, 300 ppm of aluminum sulfate solution wereadded to the mixture and mixing continued for at least five minutes.After the required mixing time, the mixing speed was increased to 150rpm. Five ppm of anionic polymer (DOL E-Z-2706 from Calgon Corp.) wereadded and then the solution was mixed at 150 rpm for two minutes,followed by mixing at 60 rpm for an additional two minutes. The stirrerwas turned off and the mixture allowed to settle for five minutes, afterwhich the clarity of the mixture was determined. If no flocculation orclarity was observed, the samples were discarded and the method wasrepeated using additional cationic polymer (up to 1200 ppm).Optimization of the aluminum sulfate may be done, but is not required.The treated samples were gravity-filtered through 25-micron filter paperand the water layer was used to determine chemical oxygen demand (COD)and turbidity.

Chemical oxygen demand (COD) was determined under limited and controlledconditions described in Standard Methods For The Examination of Waterand Wastewater, 18th Edition (1992), procedure No. 5220 D. Since many ofthe additives used in metalworking fluids are water-soluble, high CODlevels are still obtained despite splitting the surfactants of theinstant invention and obtaining distinct phase separation. Turbidity wasdetermined by the nephelometric method under limited and controlledconditions described in Standard Methods For The Examination of Waterand Wastewater, 18th Edition (1992), procedure No. 2130 B.

Treatment studies were performed using conventional nonionic surfactantsand the nonionic splittable surfactants of the instant invention. Tosimulate a typical metalworking fluid, a mixture of water,triethanolamine, orthoboric acid, sodium omadine, andethylenediaminetetraacetic acid disodium salt was used in these studies.The metalworking fluid was formulated by adding 5 (wt. percent)surfactant and 5 (wt. percent) Ergon Refining Hygold V-200 (Vicksburg,Miss.) oil to this mixture. The results of the waste treatment of thismixture are given in Table F. As Table F shows, unlike the resultsobtained for waste-water effluent from industrial laundry, there was nosignificant reduction in COD levels (examples 1-6) by using theprocedure described hereinabove for this metalworking fluid formulationwhich contains a nonionic splittable surfactant of the instantinvention. Likewise, the same formulation containing a conventionalnonionic (e.g., Tergitol® NP-9) surfactant was not treatable undersimilar conditions (examples 7-12). These results suggest that morestringent conditions are required to effect phase separation ofmetalworking fluids due to complex matrix effects which are not presentin industrial laundry wastewater effluent. These matrix effects may beovercome by the use of other components in the formulation which willnot interfere with the phase separation, and/or will aid in the phaseseparation (e.g., silicates).

In order to determine the efficacy of the nonionic, splittablesurfactants for metal cleaning, the following soak metal cleaningprocedure was run and compared to standard commercial surfactants.

Stainless Steel 304-2B Alloy coupons (Stock No. SS-13) were purchasedfrom The Q Panel Company, Cleveland, Ohio. A {fraction (1/16)}-inch holewas drilled in the coupon centered on one end so the coupon could hangvertically. Prior to use, the coupons were precleaned by two differentmethods. Procedure A used a methanol/potassium hydroxide solution. Thepanels were soaked overnight in the solution, rinsed with tap water,acetone, and allowed to dry at room temperature. Procedure B used adishwashing liquid/water solution with a scrub brush. After cleaning,the coupons were rinsed with tap water, dipped in methanol, rinsed withacetone, and hung to dry at room temperature. The precleaned couponswere weighed on an analytical balance to 4 decimal places (0.0000 g).The coupons were soiled by immersing 80-85% (approx. 2.5 inches) of thecoupon in test oil, followed by a vertical hang for one hour. After thistime, the excess oil bead at the bottom of the coupon was wiped off witha 1-inch, sponge-type paint brush. The coupon was then reweighed todetermine the amount of oil residue on the panel. Solutions of builders,solvents and surfactants were used as the cleaning media. Typically, a1-L aqueous solution with the following formulation was prepared: 0.1wt. percent sodium hydroxide, 0.1 wt. percent of surfactant, 0.1 wt.percent of sodium metasilicate (anhydrous), and 0.1 wt. percent ofsodium carbonate. The solutions were placed in beakers in a bathregulated to the desired temperature (+/−2_C.). A typical range oftemperatures was 40, 60 and 80° C. Soiled coupons were hung on therotating maechanisms and immersed in the solutions for cleaning.Rotation of the coupons was at 15+/−2 rpm. The wash cycle was 5 minutesor less, followed by a rinse in distilled water. The distilled water wasrun into a 1000-ml beaker and the coupon was rinsed in the beaker insuch a manner as not to contact the flow of water (which might haveaided in the additional removal of some of the oil). After rinsing, thecoupons were again hung vertically and allowed to air-dry. When dry, thecoupons were weighed to determine the amount of oil residue remaining onthe coupon after cleaning. The cleaning efficacy was determined by theamount of residue, divided by the amount of oil deposited, multiplied by100 to determine the percent oil removed.

Amount of Residue/Amount of Oil deposited×100=% of Oil removed

The results are given in Table G. As the results show, many of thesplittable nonionic surfactants of the instant invention show equal orbetter cleaning performance than conventional nonionic surfactants whichare known to be good metal cleaning agents (e.g., Triton® X-100).

TABLE 1 Polyol Diluent Catalyst Reaction Examples Aldehyde (grams)(grams) (mls) (gms) Time (hrs) Extraction A 2-Ethylhexanal (384.6)Glycerol heptane p-TsOH (0.50) 16 No (331.6) (400) B 2-Ethylhexanal(410.6) TMP* heptane p-TsOH (0.38) 21 Yes (530.2) (480) C 2-Ethylhexanal(387.2) TME** heptane p-TsOH (0.38) 7 No (432.7) (345) D Octanal (513.3)Glycerol heptane p-TsOH (0.20) 24 Yes (442.4) (314) E Decanal (625.9)Glycerol heptane p-TsOH (0.24) 16 Yes (442.1) (352) F Propyl butylacrolein (231.0) Glycerol heptane p-TsOH (0.2) 16 No (165.8) (369) G2-Propyl heptanal (630.2) Glycerol heptane p-TsOH (0.30) 19 No (442.1)(422) H Undecanal (682.2) Glycerol heptane p-TsOH (0.31) 24 Yes (442.6)(301) I Dodecanal (737.3) Glycerol heptane p-TsOH (0.34) 24 Yes (442.3)(320) J Dodecanal (295.1) TMP* heptane p-TsOH (0.24) 17 No (202.3) (263)K C12-C13 mixed aldehydes Glycerol heptane p-TsOH (0.59) 40 No (2283.8)(1137.1) (1219) L C14-C15 mixed aldehydes Glycerol heptane p-TsOH (0.50)40 No (2285.8) (1047.9) (1272) Percent Detergency/ Distillation YieldMolecular Ethoxylate Examples ° C./mm Hg (%) Weight 3-mole 6-mole 9-mole12-mole A 190°/6 mm 96.2 202.3 94.00 66.96 62.91 59.03 B Kettle product(1) 75.0 244.4 118.18 115.45 110.26 101.77 C Kettle product 78.6 230.4 DKettle product 83.9 202.3 76.00* E Kettle product 77.9 230.3 135.6296.32 71.86 73.17 F 190-200°/6 mm 74.5 228.3 100.81 74.01 71.19 64.46 G190-200°/6 mm 80.3 230.3 121.02 112.23 82.17 82.55 H Kettle product 76.8244.3 170.93 97.95 84.31 71.57 I Kettle product 72.8 258.3 92.45 105.7993.10 72.58 J 246-261°/8 mm (2) 72.0 258.3 69.43 148.14 108.66 79.95 KKettle product 51.4 265.4 61.92 119.48 86.11 72.67 L Kettle product 62.7293.8 115.20 100.58 98.76 94.31 p-TsOH p-toluenesulfonic acidmonohydrate *TMP 2-ethyl-2-(hydroxymethyl)-1,3-propanediol **TME1,1,1-tris(hydroxymethyl)ethane (1) material refined by removing lowboiling components leaving kettle product (2) material refined byfractional distillation 2-Ethylhexanal, Octanal, Decanal, Undecanal,Dodecanal, Glycerol, TMP, TME, and p-TsOH available from AldrichChemical Company, Inc. Milwaukee, WI Propyl butyl acrolein and mixtureof isomers obtained from aldol condensation of valeraldehyde obtainedfrom hydroformylation of mixed butenes 2-Propyl heptanal obtained asmixture of isomers from mild hydrogenation of propyl butyl acroleinC12-C13 mixed aldehydes are mixtures of isomers from EniChem AugustaIndustriale C14-C15 mixed aldehydes are mixtures of isomers from EniChemAugusta Industriale

TABLE A Percent Detergency Standard Standard Exam- moles EO (1) (2) plesAcetals 3 EO 6 EO 9 EO 12 EO 9 EO 7.5 1 A 42.15 17.72 15.33 15.76 25.1217.54 2 A* 20.89 24.75 3 A** 19.24 24.23 4 B 18.90 29.46 23.26 19.8924.83 19.34 5 F 35.28 22.62 20.71 17.49 24.41 19.19 6 I 37.31 35.6033.29 30.58 40.58 38.84 7 J 33.10 29.74 40.87 34.93 39.18 38.59 8 E37.22 33.49 30.73 28.81 40.60 38.69 9 D 36.91 33.62 30.76 27.28 40.5838.69 10 G 34.73 41.57 33.26 32.60 40.96 11 H 33.00 38.00 35.44 31.5140.57 12 K 22.41 34.09 31.32 31.27 31.79 13 L 26.49 39.67 30.08 30.8132.91 *3 moles of PO added to the acetal (A) prior to 6 moles of EO **6mole EO product made using narrow molecular weight, catalyst Standard(1)- Tergitol ® NP-9 Standard (2)- Triton ® RW-75

TABLE B Ex- Detergent Composition COD (mg/l) am- Moles (wt. %) Treatedples Acetals EO a b c d e Untreated (pH 3) 1 L 6 25 30 0 35 10 3870 37702 L 6 25 0 40 25 10 3360 280 3 L 6 15 0 70 10 5 2310 480 a- surfactantb- sodium tripolyphosphate c- sodium metasilicate d- sodium carbonate e-Sipernat 50

TABLE C Detergent Composition Moles (wt. %) Percent Examples Acetals EOa b c d e Detergency 1 L 6 25 30 0 35 10 53.65 2 L 6 25 0 40 25 10 53.423 L 6 15 0 70 10 5 52.31 4 Standard (1) 9 25 30 0 35 10 35.20 5 Standard(1) 9 25 0 40 25 10 29.95 6 Standard (1) 9 15 0 70 10 5 28.02 Standard(1)- Tergitol ® NP-9 a- surfactant b- sodium tripolyphosphate c- sodiummetasilicate d- sodium caibonate e- Sipernat 50

TABLE D Ex- am- Moles Emulsion Stability Emulsion Stability ples AcetalsEO After 1 hour After 24 hours 1 K 3 emulsified emulsified/smallseparation 2 K 6 emulsified emulsified 3 K 9 not emulsified notemulsified 4 L 3 emulsified emulsified/small separation 5 L 6 emulsifiedemulsified 6 L 9 2 separate oil layers 2 separate oil layers 7 Standard(1) 4 emulsified emulsified 8 Standard (2) 6 emulsified emulsified/ 2layers 9 Standard (3) 9 2 layers not emulsified Standard (1)- Tergitol ®NP-4 Standard (1)- Tergitoll ® NP-6 Standard (1)- Tergitoll ® NP-9

TABLE E Moles Concentration Foam height (mm) Concentration Foam height(mm) Examples Acetals EO (wt. percent) Time 0 min./5 min. (wt. percent)Time 0 min./5 min. 1 A 9 0.1 (wt. %) 10/0* 1.0 (wt. %) 55/3 2 B 9 0.1(wt. %) 47/3 1.0 (wt. %) 100/12 3 D 9 0.1 (wt. %) 55/10 1.0 (wt. %)135/5 4 E 9 0.1 (wt. %) 125/7 1.0 (wt. %) 118/8 5 H 9 0.1 (wt. %) 124/201.0 (wt. %) 137/18 6 I 9 0.1 (wt. %) 111/33 1.0 (wt. %) 126/85 7 K 3 0.1(wt. %) 20/10 1.0 (wt. %) 35/25 8 K 6 0.1 (wt. %) 85/75 1.0 (wt. %)120/110 9 K 9 0.1 (wt. %) 110/85 1.0 (wt. %) 130/95 10 K 12 0.1 (wt. %)120/95 1.0 (wt. %) 155/110 11 L 9 0.1 (wt. %) 100/85 1.0 (wt. %) 130/10512 Standard 9 0.1 (wt. %) 100/90 1.0 (wt. %) 120/105 Temperature at 25°C. Standard- Tergitol ® NP-9 *Foam collapsed <30 seconds

TABLE F Observation Cationic After Treatment Exam- Moles Temp. Time Polyappear- COD (mg/l) Turbidity (NTU) ples Acetals EO (° C.) (hrs) (ppm)ance* floc** Initial Final Initial Final 1 L 9 60 2 300 4 3 3350 3380150 143 2 L 9 60 3 100 2 3 3470 3410 3 L 9 60 4 100 3 4 3100 3070 4 L 960 10 300 3 3 3520 3240 5 L 9 60 10 1200 3 2 3520 3720 6 I 60 8 300 5 23120 3130 7 Standard 9 50 3 100 5 3 2890 2780 74 37 8 Standard 9 50 3300 5 3 2890 2940 74 38 9 Standard 9 50 3 600 5 3 2890 3150 74 30 10Standard 9 60 2 100 5 3 2990 3100 74 31 11 Standard 9 60 2 300 5 3 29903000 74 35 12 Standard 9 60 2 600 5 8 2990 3290 74 28 Standard-Tergitol ® NP-9 *appearance (1-5) 1 = clear 5 = cloudy **floc (1-5) 1 =heavy 5 = no floc

TABLE G Moles Precleaning Percent Oil Examples Acetals EO ProcedureRemoved* 1 A 3 A 67 2 A 6 A 66 3 E 6 A 79 4 I 6 A 98 5 B 6 B 75 6 G 6 B84 7 G 9 B 88 8 Standard (1) 9 B 78 9 Standard (2) 10 B 83 *Average offive coupons Standard (1)- Tergitol ® NP-9 Standard (2)- Triton ® X-100

What is claimed is:
 1. A method for cleaning a hard surface which iscontaminated with hydrophobic contaminants, comprising: (a) treatingsaid hard surface to remove at least some of said hydrophobiccontaminants by contacting said hard surface with a compositioncomprising an aqueous solution of a nonionic, splittable surfactanthaving either of, or mixtures of, the formulas

 or,

of which R is hydrogen and R′ is the residue of an organic compound(substituted or unsubstituted) derived from an aldehyde of the formula

wherein R is hydrogen and R′ is the residue of an organic compound(substituted or unsubstituted) which contains a total of about 8 toabout 20 carbon atoms; X is hydrogen or the residue of a hydrophobicend-cap; Y is hydrogen, methyl, ethyl, or mixtures thereof; Z ishydrogen, methyl, or ethyl; m is 0 or 1; and n is an integer of 1 toabout 40; (b) removing an effluent stream comprising the hydrophobiccontaminants removed from the hard surface in step (a) in aqueousemulsion with said surfactant; (c) treating said effluent stream with anacidic material to reduce its pH sufficiently to cause the surfactant toirreversibly split into an aldehyde and a polyol, thereby causing thehydrophobic contaminants contained in the aqueous emulsion to bereleased from the emulsion to create a water-insoluble phase comprisingthe aldehyde and the hydrophobic contaminants and a relativelycontaminant-free aqueous phase comprising the polyol; and (d) separatingat least some of said water-insoluble phase from said aqueous phase.